Upgrade to coverage 3.7.1 and have it auto-build itself on first use.

third_party/coverage-3.7.1/coverage/collector.py

Index: third_party/coverage-3.7.1/coverage/collector.py
diff --git a/third_party/coverage-3.6/coverage/collector.py b/third_party/coverage-3.7.1/coverage/collector.py
similarity index 93%
rename from third_party/coverage-3.6/coverage/collector.py
rename to third_party/coverage-3.7.1/coverage/collector.py
index 96a9661bdd896ac3d821ecde135e6904ed4cac21..8ba7d87cd4e055b2e11efccd487bc7493f58d19d 100644
--- a/third_party/coverage-3.6/coverage/collector.py
+++ b/third_party/coverage-3.7.1/coverage/collector.py
@@ -51,13 +51,19 @@ class PyTracer(object):
         self.last_exc_back = None
         self.last_exc_firstlineno = 0
         self.arcs = False
+        self.thread = None
+        self.stopped = False
 
     def _trace(self, frame, event, arg_unused):
         """The trace function passed to sys.settrace."""
 
-        #print("trace event: %s %r @%d" % (
-        #           event, frame.f_code.co_filename, frame.f_lineno),
-        #      file=sys.stderr)
+        if self.stopped:
+            return
+
+        if 0:
+            sys.stderr.write("trace event: %s %r @%d\n" % (
+                event, frame.f_code.co_filename, frame.f_lineno
+            ))
 
         if self.last_exc_back:
             if frame == self.last_exc_back:
@@ -73,10 +79,11 @@ class PyTracer(object):
             # in this file.
             self.data_stack.append((self.cur_file_data, self.last_line))
             filename = frame.f_code.co_filename
-            tracename = self.should_trace_cache.get(filename)
-            if tracename is None:
+            if filename not in self.should_trace_cache:
                 tracename = self.should_trace(filename, frame)
                 self.should_trace_cache[filename] = tracename
+            else:
+                tracename = self.should_trace_cache[filename]
             #print("called, stack is %d deep, tracename is %r" % (
             #               len(self.data_stack), tracename))
             if tracename:
@@ -117,18 +124,24 @@ class PyTracer(object):
         Return a Python function suitable for use with sys.settrace().
 
         """
+        self.thread = threading.currentThread()
         sys.settrace(self._trace)
         return self._trace
 
     def stop(self):
         """Stop this Tracer."""
+        self.stopped = True
+        if self.thread != threading.currentThread():
+            # Called on a different thread than started us: we can't unhook
+            # ourseves, but we've set the flag that we should stop, so we won't
+            # do any more tracing.
+            return
+
         if hasattr(sys, "gettrace") and self.warn:
             if sys.gettrace() != self._trace:
                 msg = "Trace function changed, measurement is likely wrong: %r"
                 self.warn(msg % (sys.gettrace(),))
-                #--debug
-                #from coverage.misc import short_stack
-                #self.warn(msg % (sys.gettrace()))#, short_stack()))
+        #print("Stopping tracer on %s" % threading.current_thread().ident)
         sys.settrace(None)
 
     def get_stats(self):
@@ -161,7 +174,7 @@ class Collector(object):
         """Create a collector.
 
         `should_trace` is a function, taking a filename, and returning a
-        canonicalized filename, or False depending on whether the file should
+        canonicalized filename, or None depending on whether the file should
         be traced or not.
 
         If `timid` is true, then a slower simpler trace function will be
@@ -205,7 +218,7 @@ class Collector(object):
 
         # A cache of the results from should_trace, the decision about whether
         # to trace execution in a file. A dict of filename to (filename or
-        # False).
+        # None).
         self.should_trace_cache = {}
 
         # Our active Tracers.